Mexico has supplanted China as the main source of goods, but imports keep climbing.

Mexico and Canada are the United States’ top two trading partners, accounting for nearly 30% of trade volumes.

Trump, who takes office on Jan. 20, said he would impose a 25% tariff on imports from Canada and Mexico until they clamped down on drugs, particularly fentanyl, and migrants crossing the border, in a move that would appear to violate a free-trade deal.

While the announcement is almost certainly bluster to bring attention to illegal immigration and fentanyl smuggling, there are several reasons why it is so risky.

The tariffs, if implemented, could dramatically raise prices for American consumers on everything from gas to automobiles to agricultural products.

Economists worry that Trump's tariff plan will raise the prices of a range of imported goods, from cars to electronics.

Chinese firms are on edge and so are some of their US partners. Markets are relatively muted, though the yuan is down.

By Joe Cash BEIJING (Reuters) -China attacked U.S. President-elect Donald Trump's pledge to slap additional tariffs on Chinese goods over fentanyl flows, saying his incoming administration was pushing the blame for America's opioid crisis onto China.

President-elect Trump’s emphatic promise of new tariffs is sharpening the debate over how he will handle the economy. It’s likely the single most important domestic issue of his second term. Trump is poised to enjoy almost perfect timing in taking the reins of an economy on the rise.